Method of producing threadcutting chasers



Jan. 2, 1951 R. M. sTRlcKLAND Erm. 2,536,854

METHOD 0F PRODUCING THREAD-CUTTING CHASERS Filed Nov. 25, 1946 2sheets-sheet 1 l! lll ,y

Jan. 2, 1951 2,536,864

R. M. STRICKLAND ETAL METHOD OF PRODUCING THREAD-CUTTING CHASERS FiledNov. 23, 1946 '2 Sheets-Sheet 2 Patented Jan. 2, 1951 UNI-T ED STATESATENT o-FFICE METHOD OF PRODUCING THREAD- lCUTTING CHA-SERS ofMassachusetts ApplicationNovember 23, 1946, Serial No. 711,888l

6 Claims.. (C1. 51- 288) The' present invention relates in general tothread-cuttingl tools and more especially to chasers which aref adaptedto be m'ountedf in sets of twoor moreY inY self-operating die-heads forcutting. threadsion work-pieces.

An obiectof. they present inventionis toprovide air improved method forproducing thread-cutting chasers.

A. further object of the: invention is to provide an improved; methodforl producing thread-cutting chasers: which. is economical and whichprod-uces superior chasers in: comparatively few operations.

A still further object. ofthe' presentl invention is to: provide a.novelmethod of the character referred tos whereby the thread-cuttingteeth of partially-completed chasers are used as reference-surfaces for.forming the operating-grooves of the-chasers.

A still` further obiect of the invention. is to-pro- Videa novel. methodof the character referred to, whereby a. relatively largel number ofchaserbla-nks may be subjected simultaneously tol-"mishing operations ofthe greatest accuracy.

With the above and` other objects in View, as willappear to7 thoseskflledv iny the art from the present disclosure, th-isinventionincludes all features inA thev said. disclosure which are novel over thepriorart.

In the accompanying drawings,v in which certain modes of carrying out.the present invention are shown. for illustrativepurposes :V

Fig. 1 is a perspective view of a hardened and tempered. Chaser-blank.which. has. been roughground toV a. predetermined. thickness. and heightand has had. its ends squared;

Fig.. 2 is. a perspective view. of the hardened Chaser-blank. shown inFig'. l after. the blank has been ground to. finished thickness.`- andYprovided with a. partally-ground. rake andv cutting-tace. This. is the.stage at. which. the blanks are. carried in stock;

Fig. 3 is' a perspective view of. a.. chaser-blank whichhas beentakenfrom. stock, therst operation chaser-blank.. to. its. finished;over-alt length with a radius at its rearl end.;

Fig. 4i: represents the chaser-blan-k of Fig. 3 having thread-cuttingteeth. ground in its: cntting-edge;

Fig. 5 is a schematic plan View of the improved method of gang-grindingthe longitudinal. keyways inthe chaser-blanksof Fg. 4,; e

Fig. 6 is a. sectional. elevation of. theganggrinding assembly takenonline- 6.-l. of. 5;

performedthereonconsisting off gr-'nding the Fig. 7 is a sectionalelevation onV line 'l--l of Fig. 5;

Fig. 8 is a perspective view` of a Chaser-blank following the grindingof its longitudinal keyway;

Fig. 9 is a schematic plan View of the improved method of gang-grindingthe transverse controlgrooves of the chaser-blanks;

Fig. 10 is a sectional' elevation. of the ganggrinding assembly ontheline l-l' of Fig. 9;

Fig. 1'1 is a sectional elevation on lin-er l-l-H of Fig. 9';

Fig. l2 isa perspective' View ofa Chaser-blank following the grinding ofits transverse controlgroove; and

Fig. 13 is a perspectiveY View of the chaserblank showing the clearanceformed at opposite yends of one wall ofthe transverse control-groove andthe bevels formed onl the irst andi last thread-cutting teeth;

Before proceeding with a detailed description of one mode ofY carryingout the present invention, it may here be pointed out that in order toform accurate threadsl on a work-piece, the control-groove, which isformed in the bottom edge of each individual: Chaser, mustV be locatedwith the utmost accuracy ink relation tothe respective thread-cuttingteeth, while the control-grooves of a given set of chasers must be veryaccurately located with respect to each other. One of the numeroussources ot manufacturing difficulties in connection with the productionof threadcutting chasers, by present-daymeth'ods, is that of providingacontrol-groove which will be so accurately located as toinevita-blycause thev production of accurate' threads on a work-piece. Moreover,present-day methods have` been characterized by prescribed. stepswhichmake it infeasible to stock large quantities of partiallycompletedblanks, pending further's'elective operations thereon, each chaser-blankrequiring, in general, individual handling.

Referring to the drawings which show in succession the principal stepsfollowed in carrying out the improved method of this invention, theChaser-blanks are formed from stock material which, as shown at lea inFig. l, comprises a substantially-rectangular block of steel cut from alength of soft steel stock and subsequently hardened and tempered, 01-cut from a length of hardened and tempered steel stock. The latter isthe preferred way of supplying the chaserblank stock material, althoughthe hardening of soft steel stock may be |equally successful. The blankita has beenV subjected to several preliminary flat-grindingyoperations. which include Vbe of the order of 1/16.

rough-grinding the blank to a predetermined thickness and height,squaring the ends of the blank and removing burrs from the corners and yedges thereof, all of which operations are performed by standardtechniques known in the art. The blank |5a comprises top and bottomsurfaces IG and l1 respectively, a rear end I8 opposite which is thecutting-edge |9 which is adapted, as hereinafter described, to embodythe thread-cutting teeth of the chas-er-blank. The side of the blank isreferred to as the keyway side, while the opposite side 2| of the blankis hereinafter referred to as the reference side or reference surface ofthe blank.

Following these preliminary grinding operations, the blank |5a is thenground to finished thickness, as shown at ib in Fig. 2, by conventionalflat-grinding operations. It is preferable, though not necessary, to thesuccess of the invention, to rst flat-grind the reference-surface 2| ofthe blank and thereafter to complete the grinding operations on theother surfaces i5, |1 and 2B of the blank by using the surface 2| forreference purposes. Additional steps taken in forming the blank |519include rough-grinding the cutting-face 22 of the blank and the rake 23on the cutting-edge IS thereof. Moreover, chasers of the type disclosedand described herein by way of illustration are known to the trade asprojection-chasers, the chaser shown in the drawings being a 9/16 D typeprojection-Chaser, and are characterized by shoulders or projections 24adjacent the cutting-edges of the blanks. These projections 2li arepreferably formed by grinding off the tops I6 of the blanks to formflats 25 therealong.

In accordance with the improved method of this invention, the over-alllength of each chaserblank which has been processed to stage 15b of itsmanufacture is greater than the maximum lengths of all standard types ofchasers and in this form the chasers |5b are adapted to be stocked. Whenthe Chaser manufacturer is ordered to make up a set of chasers accordingto certain specifications as, for example, a 9/16 D typeprojection-chaser, the required number of Chaser-blanks |51) are takenfrom stock and processed, as hereinafter described, to produce afinished set.V For the purpose of clarity, the description which followswill deal with the sequence of operations performed on one blank of aset but it will be understood that in practice a plurality of blanksrequired to form a Set of -chasers are processed simultaneously.

Assuming a blank lh has been taken from stock, the first operationperformed on the blank is that of reducing the over-all length of theblank to a standard length for a specific type of chaser. By way ofillustrating t-he over-all length of each blank Ib as stocked, theamount of metal which must be removed from the rear end i8 thereof toform the blank |50 of standard lengt-h for a 9/16 D typeprojection-Chaser may Ths grinding operation may be a flat-grindingoperation, but is'generally a radius-grind, so as to provide a,cylindrical surface of revolution 2i; on the rear end of the blankwhereby the rear end thereof will present an arcuate surfacesubstantially concentric with the periphery of the Chaser-holder ordiehead. The preferred length of the radius of the surface 26 issubstantially 2 but it will be appreciated that the 2 radius is typicalfor the -type of projection-chasers identified above and that thisdimension will vary, depending upon the specifications of the chaserbeing manufactured andI the size of the die-head.

The next operation on the blank 23e is that of grinding thethread-cutting teeth 21 in the raked cutting-edge Z3 thereof to formt-he blank ld. This operation is performed by engaging the flatgroundreference-surface 2| of the blank on the magnetic chuck or equivalentsupporting-surface of a grinding machine and moving the rakedcutting-edge 23 of the blank into engagement with the periphery of arotating multiple-groove grinding-wheel of the type in general use forthread-grinding purposes. It will be appreciated that after grinding thethread-cutting teeth 21 in the raked cutting-edge 23 of the blank ld(see Fig. 4), the blank is adapted for use only in cutting a thread of aspecific diameter and pitch. Consequently, it is proposed to utilize theteeth 21 of the blank ld as the reference-surface for subsequent nishingoperations, the first of which may be that of grinding the longitudinalkeyway in the side 2i) of the blank.

Referring to Figs. 5, 6 and '1, the proposed method of grinding thelongitudinal keyway is by a gang-grinding technique wherein a pluralityof blanks |56! are assembled in end-to-end relationship on thereciprocable platen or magnetic chuck 28 of a grinding-machine, theblanks being supported securely thereon by suitable guides 29 andspacer-blocks 38, in a manner well known to the art. The assembledblanks are then adapted to be moved longitudinally in asubstantiallyhorizontal plane beneath the lower edge of a grinding-wheel3| which is mounted on a horizontal shaft and adapted to rotate in avertical plane parallel to the longitudinal path of movement of theblanks.

As indicated in Fig. 6, the grinding-wheel 3| is adapted to grindcontinuously a longitudinal keyway 32 of rect-angular cross section insuccessive blanks throughout the lengths of their sides 2O and in onesingle pass of the blanks relative to the rotating grinding-wheel. Asshown in Fig. '7, the cross section of the periphery of thegrinding-wheel 3| is substantially rectangular, having been dressed tothe exact dimensions required for the keyway 32, and hence is adapted togrind simultaneously from solid all three surfaces of the longitudinalkeyway to finished dimensions, both the side walls 33 and the bottomwall 34 of the keyway being ground to a mirror-like finish. TheChaser-blank is now in the form shown at stage |5e in Fig. 8.

The next succeeding step in the manufacture of the Chaser-blank is thatof grinding the transverse control-groove 35, sometimes referred to asthe cam-lug slot, in the bottom |'l of the blank. Referring to Figs. 9,l0 and 11, it is proposed to grind the transverse control-grooves 35 ofa plurality of blanks |5e by gang-grinding and to this end, the blanks|56 are adapted to be assembled on the reciprocable platen or magneticchuck 36 of a grinding machine and secured thereon by a guide 31 andspacer-blocks 38. In assembling the blanks |5e on the platen 3S, thelongitudinal axis of each blank is adapted to make an acute angle p withrespect to the plane of rotation of the grinding-Wheel 39, the angle pbeing equal to the angle of Obliquity which the longitudinal axis of thetransverse control-groove 35 of each blank is adapted to make relativeto the longitudinal axis thereof. Moreover, as assembled on the platen36 of the grinding machine, the teeth 21 of the blanks are adapted toengage the guide 31 so that the points of the teeth constitutereferasse, een

groove.l 35 or' each blank' at precisely' the@ right distance from. itsthread-cutting.v teeth.. llhei con.- trolgroovesr 35i are. adapted tovbe: ground` in the bottoms I6; of: the. blanks. byfa single pass of the.

assembled` blanks beneath the edge;` of' the.y ro.- tating.grinding-wheel'. 39, the; periphery ot which isz dressed' to the exact;shape. and' dimensions. required for the control-grooves. 3,5., as shownin llig.'` 11,.wherebyf the. two; space'df` paralleli Walls; 4.0andathe; bottoni Wall 'l l; ofi each groovefare; ground simultaneouslyfrom solid, toi nnished dimensions andi with a mirrorelikegf Thegrinding of, the@` t'ransyerse control-groovey 35 may'beregafrded: ascompleting the major grinding operationspier.- formed. on: the. blank.|259.; the. latter now being. in the form shownat stagev iy-finFig-1:21.

TheneXt succeeding: grinding.y operation. performed' on they blanks-|51? is. that-of: rounding-ofi the opposite: endsY respectivelyl of oneWalll ofl the transverse'.control-groove*35 to providev clearance,the'latter. WallV beingf hereinafter termed; the. advancing'wall of thecontrol-groove, its`- opposite wall being referred. to,l as,theretractingfY Walle. Ther-founded surfaces 42 at opposite ends ofv theadvancing Wall. 4.0 of the control-grooves 3-5V are formed. by aradius-grinding: operation, and; it Willzbenoted that theinner. ends' oftherespective roundedsurfaces. 42 do not join but blend intothe oppositeendsy respectively ot anat 13: hereinafter termedr a telltale" orwitness mark. 'I-Theilatter. constitutes-a. portion: oftheifadvancing-Wallof the controlegroovewhich-has been untouched orunchanged. by the; radius-grinding operations, so that. the".-ac'curacyf ot the' control-gfronvev is. not impaired. and. inf the,embodiment.y shown. is. substantiallyl 11e wide; In' forming thelroundedsur.- faces 42 at oppositezends. respectively of. the.- ad.- vancingvWall. of the control-groove, the teeth 2l of the blank are againi used'as reference-surfaces in setting up the blank in proper relation to theradius-grinding. Wheel'. Following; the grinding of theroundedclearance-surfaces.42. of. the controlgroove 35, the lead and lagthread-cutting teeth are beveled as at 44 in Fig. 13, after whichseveral other finishing operations are performed to produceY the blanki5g, among which are the steps of nish-grinding the rake. of theteetlfr1 2:1 and chamfering all corners and edges: of the cha-ser.

All'. of these latter operations are conventional andare not'numberedamong. the-.novelsteps of the present invention.

From the foregoing disclosure,` it will appear that in. accordance withthe novel method@ of. this invention, iinished chasers may be quicklyand accurately formed from hardened: and tempered steel blanks-.Whichhave been-previously stocked in partially-completed form. Moreover,relatively few-operations are required to com-plete the chasers, theprincipal operations being those of grinding the teeth thereon andthereafter using the ground teeth as reference-surfaces for grinding thelongitudinal keyvvay and transverse controlgroove of the blank, theopposite ends of which are subsequently rounded, as described above.

The improved method of this invention is adapted to form both regularand projection-type chasers with equal facility, and surpasses ineconomy and rate of production any method which has been used previouslyfor the manufacture of Chaser-blanks. `This latter aspect of theinvention is due primarily to the novel concept of utilizing thethread-cutting teeth of hardened partially-completed blanks taken fromstock, as reference-surfaces for subsequent nishing operations;A as aconsequence. of which: 'am inventory consisting ot a relatively small=number'of partiallyecom'pleted blanks. be, kept, any one'. ofvvhi'chmaylbe subsequently nished tov any of: the standard chaserf dimensions; Itshonldt be noted that heretofore. it. has. been impracticable to..-store partially-completed", blanks, inasmuch; as all suchz blanks, byprevious methods et! manu'.- facture,v have,l off: necessity; beenrestricted in: use to a specificitypesof chaser'andhence, in orderytohave partiallyeni'shed, chasers, available for iinishing operain'onsfora-llstandard types of chasers, avery: large, expensive: and:uneconomical inventory. hasbeen required..

The: invention` may be.; carried out. in other. specifica Ways thanxthose; herein set. forth Without departing from theis-piritlfandessential characteristics of the invention; and the presentembodimentsara. therefbre, to be. Considered: in all respeets asillustrative; and not. restrictive; and, all changes coming withinthemeaning and equivalencyrangefof the appended: claims are intendedtobe embraced. therein'.

W e: ola-ima:

l.. '-hier method for producing a set of threadcutting chasers, whichmethod. includes a plurality of' successive steps performed in thefollowing predetermined sequence: grinding in.V a singlel operation.fiat-ground reference surfaces on: a set of previously hardenedl and'tempered chasers-blanks.; subsequently grinding; in' a' single operationplurality of thread-cutting teeth in corresponding surfaces of thesai-il set. of hardened and@ temperedchaser-bianks other than. the said.nat-ground reference; surfaces; thereafter simultaneouslyy grinding. a.single; operation; all three; walls.: oi longitudinal keyways invcorre,- spondi'ng surfaces or the: Said. set. of: chaserblanlszsa otherthan the. said. surfaces thereof formedL Withthe thread-cutting: teeth;and then using the points of said. teeth as. reference surracestosin'inltaneousl'yl grind. in a single operatiorr all' three Walls oftransverse con-trolgroottes. in corresponding surfaces of the said setot Chaser-blanks other than the said surfaces thereof. formed Withthesaidthread-cuttingteeth and: the: said, longitudinal keyways`respectively.

2.. The method for producing a set of threadcutting: chasers.. whichmethod includes av plurality of successive steps performed in thefollowing. predetermined sequence: grinding in a single operation.nat-ground reference surfaces or; a set ofv previously hardened. andtempered chasser-blanks.;- subsequently grinding in a single operation aplurality of. thread-cutting teeth in corresponding surfaces ofv thesaid set of hard.- cnedl andi tempered-i Chaser-blanks other than the.said? itat-ground. reference surfaces.; thereafter' simultaneouslygrinding: in a single operation all three walls of longitudinal keyvvaysin corresponding surfaces of the said set of chaserblanks other than thesaid flat-ground reference surfaces and the said surfaces formed withthe thread-cutting teeth; and then using the points of said teeth asreference surfaces to simultaneously grind in a single operation allthree Walls oi transverse control-grooves in correspending surfaces ofthe said set of chaserblanks other than the said surfaces thereof formedwith the said thread-cutting teeth and the said longitudinal keywaysrespectively.

3. The method for producing a set of threadcutting chasers, which methodincludes a plurality of successive steps performed in the followinglpredetermined sequence: grinding in a single operation flat-'groundreference surfaces on a set of previously hardened and temperedChaser-blanks; subsequently grinding in a single operation a pluralityof thread-cutting teeth in corresponding surfaces of the said set ofhardened and tempered Chaser-blanks other than the said flat-groundreference surfaces; thereafter simultaneously grinding in a singleoperation all three walls of longitudinal keyways in correspondingsurfaces of the said set of chaser-blanks other than the surfacesthereof formed with the said thread-cutting teeth; thereafter using thepoints of said teeth as reference surfaces to simultaneously grind in asingle operation all three walls of transverse control-grooves incorresponding surfaces of the said set of Chaser-blanks other than thesaid surfaces thereof formed with the said threadcutting teeth and thesaid longitudinal keyways respectively; and then using the points ofsaid teeth as reference surfaces to grind the opposite ends of onecorresponding wall of each of the said control-grooves to provideclearance at the opposite ends thereof and to leave the intermediateportions of the said corresponding walls unchanged. f

4. The method for producing a set of threadcutting chasers, which methodincludes a plurality of successive steps performed in the followingpredetermined sequence: grinding in a single operation flat-groundreference surfaces on a set of previously hardened and temperedchaserblanks; subsequently grinding in a single operation a plurality ofthread-cutting teeth in corresponding surfaces of the said set ofhardened and tempered Chaser-blanks other than the said fiat-groundreference surfaces; thereafter simultaneously grinding in a singleoperation all three walls of longitudinal keyways in correspondingsurfaces of the said set of Chaser-blanks other than the saidflat-ground reference surfaces thereof and the said surfaces formed withthe said thread-cutting teeth; thereafter using the points of said teethas reference surfaces to simultaneously grind in a single operation allthree walls of transverse control-grooves in corresponding surfaces ofthe said set of Chaser-blanks other than the said surfaces thereofformed with the said thread-cutting teeth and the said longitudinalkeyways respectively; and then using the points of said teeth asreference surfaces to grind the opposite ends of one corresponding wallof each of the said control-grooves to provide clearance at the oppositeends thereof and to leave the intermediate portions of the saidcorresponding walls unchanged.

5. A method for producing a set of threadcuttingI chasers, which methodincludes a plurality of successive steps performed in the followingpredetermined sequence: grinding in a single operation fiat-groundreference surfaces on a set of previously hardened and temperedchaserblanks; subsequently grinding in a single operation a plurality ofthread-cutting teeth in corresponding surfaces of the said set ofhardened and tempered Chaser-blanks other than the said fiatgroundreference surfaces; and thereafter using the points of saidthread-cutting teeth as reference surfaces to simultaneously grind in asingle operation all three walls of transverse controlgrooves incorrespondingI surfaces of the said set of Chaser-blanks other than thesurfaces thereof formed with the said thread-cutting teeth.

6. The method for producing a set of threadcutting chasers, which methodincludes a plurality of successive steps performed in the followingpredetermined sequence: grinding in a single operation flat-groundreference surfaces on a set of previously hardened and 'temperedchaserblanks; subsequently grinding in a single operation a plurality ofthread-cuttingr teeth in correspondingI surfaces of the said set ofhardened and tempered chaser-blanks other than the said flatgroundreference surfaces; thereafter using the points of said thread-cuttingteeth as reference surfaces tov simultaneously grind in a singleoperation all three walls of transverse control-grooves in correspondingsurfaces of the said set of chaser-blanks other than the surfacesthereof formed with the thread-cutting teeth; and then using the pointsof said thread-cutting teeth as reference lsurfaces to grind theopposite ends of one corresponding wall of each of the control-groovesto provide clearance at the opposite ends thereof and to leave theintermediate portions of the said corresponding walls unchanged.

ROYCE M. STRICKLAND. JOHAN V. ARVIDSON.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 798,352 Leonard Aug. 29, 19051,271,495 Ward July 2, 1918 1,555,853 Higgins Oct. 6, 1925 1,557,005Bath Oct. 13, 1925 1,603,446 Breitenstein Oct. 19, 1926 1,694,560 ParishDec. 11, 1928 1,743,116 Cook Jan. 14, 1930 1,793,727 Walker Feb. 24,1931 1,931,445 Aker Nov. 20, 1934 2,096,422 Brunner Oct. 19, 19372,144,987 Miller Jan. 24, 1939 2,394,645 Turner et al Feb. 12, 1946

